Developer roller coating means and guide for electrostatic copying machine



March 17, 1970 R. J. BARTUSEK 3,500,793

DEVELOPER ROLLER COATING MEANS AND GUIDE FOR ELECTROSTATIC COPYINGMACHINE y Filed Oct. 50, 1967 3 Sheets-Sheet 1 Int/6771277" Robert Jfiarzusek.

March 17, 1970 R. J. BARTUSEK DEVELOPER ROLLER COATING MEANS AND GUIDEFOR ELECTROSTATIC COPYING MACHINE 3 Sheets-Sheet 2 Filed Oct. 30, 1967 kT? w mm n5 1 I r m R 5512M WM q g March 17, 1970 R. J. BARTUSEK3,500,793

DEVELOPER ROLLER COATING MEANS AND GUIDE FOR ELECTROSTATIC COPYINGMACHINE Filed Oct. 50, 1967 3 Sheets-Sheet 5 fnzierdr- Foberz JBarzusek.

United States Patent Office 3,500,793 Patented Mar. 17, 1970 U.S. Cl.118637 7 Claims ABSTRACT OF THE DISCLOSURE Apparatus for use in thedevelopment station of electrostatic copying machines using liquiddeveloper compositions, to improve development of a copy sheet bearing alatent electrostatic image. In particular, this invention relates toimprovements in apparatus for coating a developer roller with liquiddeveloper for subsequent application to the image bearing copy sheet.

Conventional electrostatic copying, wherein a copy sheet bearing alatent electrostatic image is subjected to a developing medium, can bebroadly divided into two categories based upon the characteristics ofthe d veloping medium. The first category utilizes a granularelectroscopic powder which may be either cascaded over the latent imageor applied by creating a powder cloud adjacent thereto. The secondcategory, to which the invention relates, uses liquid developers ortoners which comprise a liquid vehicle carrying a finely divided opaquepowder.

The advantages of liquid developers over dry powder developers withrespect to total development time and the degree of control of thedeveloping process, are well known by those familiar with the art.

The development step is probably the most vexatious and critical step inthe electrostatic copying process. It is during this step that theliquid developer is physically applied to the copy sheet byelectrostatic attraction. The opaque particles in the liquid developeradhere to the sheet establishing a visible light and dark patterncorresponding to the latent electrostatic image. The development steptakes place at a development station which may include a rotating drumor roller, called a developer roller. The surface of the developerroller is coated with liquid developer and the image bearing copy sheetis transported into developer application relationship with the coatedsurface.

The liquid coating over the surface of the developer roller directlyaffects the quality of. the reproduced image, thus its parameters mustbe accurately controlled for consistent high quality copying. Theparameters involved include a copious supply of liquid developer forminga heavy coating over the roller surface for obtaining high contrastimages. The coating should have a uniform thickness along the length ofthe roller to obviate streaking the image bearing sheet. Also, thecoating should comprise fresh liquid developer to prevent repeatedlyapplying developer to the copy sheet which has been depleted of theimage forming opaque powder.

In addition to the above parameters, care must be taken to preventliquid developer from reaching the image bearing sheet in any othermanner than by normal application from the developer roller. Splashingand fortuitously misdirected droplets of liquid developer must be heldto a minimum and if such droplets occur, the image bearing sheet must beshielded from their path.

This invention obviates the above-mentioned problems and difliculties byutilizing a novel combination copy sheet guide and shield, and a novelliquid developer nozzle construction for evenly applying a heavy coatingof fresh liquid developer to the surface of the developer roller. Theroller surface carries the fresh coating to the image sheet forsubsequent application to one surface thereof.

The nozzle is positioned closely adjacent the developer roller andsubstantially close to the area where liquid developer is transferredfrom the roller surface to the image bearing sheet. The peripheralsurface of the roller is coated with liquid developer by rotating itthrough a longitudinal pool of liquid, the pool being formed by a cavityin the nozzle and by a segment of the roller surface. In addition, anarcuate shoe is disposed adjacent the roller surface and a gaptherebetween assists in wetting the surface with liquid developer.Finally, a low velocity stream of liquid developer is directed towardthe area of the roller surface where the liquid developer is applied tothe copy sheet. This low velocity stream assists in purging a portion ofthe partially depleted liquid developer from the roller surface,allowing a fresh coating to be carried to the copy sheet.

Accordingly, the primary object of this invention is to provide meansfor improving the developing step in electrostatic copying machines.

Another object of this invention is to provide improved application ofliquid developer from a developer roller of an electrostatic copyingmachine, to a copy sheet bearing a latent electrostatic image.

Another object of this invention is to provide means for maintaining acopious coating of liquid developer on the surface of a developer rollerfor subsequent transfer, upon demand, to a copy sheet bearing a latentelectrostatic image.

A further object of this invention is to provide means for maintaining auniformly heavy coating of liquid developer on a developer roller in anelectrostatic copying machine, for subsequent transfer, upon demand,directly to a copy sheet bearing a latent electrostatic image.

It is also an object of this invention to provide means for maintaininga fresh coating of liquid developer on the developer roller of anelectrostatic copying machine.

Other objects of this invention will become apparent from anunderstanding of the following description taken in conjunction with theaccompanying drawings wherein:

FIG. 1 is an elevational view of the invention including a copy sheettransport system therefor.

FIG. 2 is a top plan view of the invention and copy fsheet transportsystem taken along lines 2-2 of FIG. 1.

FIG. 3 is an enlarged three dimensional perspective view of the liquiddeveloper nozzle and associated developer roller.

FIG. 4 is a greatly enlarged cross-sectional elevational view takengenerally along line 44 of FIG. 3 showing the surface of the developerroller in detail.

With reference to FIGS. 1 and 2 there is shown a portion of a housingfor a development station 8 of an electrostatic copying machine. Thehousing includes a top wall 10 having a sloping frontal portion 12, arear wall 14, side walls 16 and 18, and a bottom wall 20. An opening 21is provided through frontal portion 12 for exiting of a copy sheet,designated by reference numeral 22. As best seen in FIG. 1, the copysheet enters the development station through an entrance guide 24comprising upper and lower guide walls 26 and 28 respectively. The copysheet is picked up by a nip 29 formed between a pair of rotatingentrance rollers 30 and 32 which carry the sheet through a V-shapedcombination sheet guide and shield 34 and across the top surface of arotating developer roller 36. The orientation of the copy sheet withrespect to the roller surface and the physical charcateristics of thedeveloper roller will be discussed in detail below.

From the develop roller, movement of the copy sheet is assisted byfrictional contact between the top surface thereof and a roller 38. Thisfrictional contact directs the copy sheet over a drying roller 40 havinga peripheral surface 41, which moves in a direction opposite to thedirection of the copy sheet. Surface 41 removes superfluous liquid fromthe underside of the copy sheet. Operation of the drying roller and anassociated doctoring blade 42 is more fully described in a copendingapplication of Casimir S. Samczyk bearing Ser. No. 632,746, filed Apr.21, 1967 and assigned to the same assignee as the subject application.

Further progress of the copy sheet through the development sectionincludes a curved direction changing guide 44 which'deflects thehorizontally moving paper upwardly and directs it to a nip 45 between apair of combination pressure and transport rollers 46 and 48 whichremove additional excess liquid. The copy sheet is subsequently fedthrough an exit guide 50 and is finally advanced by a pair of exitrollers 52 and 54 through the exit opening 21 provided in frontalportion 12.

The above description is of a transport system for feeding a copy sheetbearing a latent electrostatic image into the development station of anelectrostatic copying machine, advancing the sheet through a guide, pasta developer roller, over a drying roller, changing its direction ofmovement, and finally guiding the sheet through an exit opening to theexterior of the machine.

Referring now to FIGS. 3 and 4 in addition to FIG. 1, the developerroller 36 and the liquid developer nozzle will be described in detail.

The developer roller is fabricated of electrically conductive materialsuch as steel. It is supported for rotation on a concentric shaft 51having a center-line or axis 52, and is journalled to side walls 16 and18 at 53 and 55 respectively. The peripheral surface of the developerroller comprises a plurality of closely spaced circular grooves 57separated by circular ridges 57a which, when rotating, distribute theliquid developer along the roller length. The height and width of thegrooves and ridges are extremely small, being measured in thousandths ofan inch, although the exact dimensions do not appear to be critical. Asbest seen in FIG. 4, the crests or tops of ridges 57a are preferablyflat to present a substantial area of liquid developer coating to thecopy sheet.

The grooves and ridges of the developer roller are coated with liquiddeveloper by a longitudinal nozzle assembly generally referred to byreference numeral 56. The nozzle assembly includes a shoe 58 having anaccurate wall 60 complementary in shape to the curved surface ofdeveloper roller 36 and disposed closely adjacent thereto to define aspace or a gap 62. Nozzle assembly 56 also includes an interior plenumchamber 64 extending its entire length and an inlet pipe 65communicating with the chamber for admitting liquid developer. A liquiddistribution baflle 67 is disposed in the plenum chamber directly abovethe junction of the inlet pipe to insure sideward dispersion of theliquid developer and to provide an even liquid flow across the length ofthe chamber.

An opening is provided through the top wall of the plenum chaber whichleads to a serpentine path 66 terminating in a longitudinal nozzlerestriction or orifice 68. From the orifice, liquid developer isdischarged into a longitudinal cavity 70 defined by the surface ofroller 36, a baflle 72 and a pair of supporting sidewalls 74 and 76. Thecavity is disposed substantially above the shaft 51 of developer roller36 and contains a longitudinal liquid pool 71 through which the groovedand ridged surface of the developer roller moves to capillarily pick upits coating. The copy sheet is subsequently directed over the top of theroller, a fraction of an inch above its surface. Ideally, the lowersurface of the copy sheet floats over the roller, riding on the liquiddeveloper coating.

Liquid developer is normally stored in a container 78 disposed directlybeneath the nozzle and developer roller.

A supply of liquid developer 80 is maintained in the tank at an adequatelevel to supply a recriculating pump 82 having a pump inlet 83. The pumpdelivers liquid developer through a flexible walled conduit 84, having athrottling clamp 85 secured thereabout, to inlet pipe 65 of the nozzle.Regulation of the quantity of liquid developer delivered to the nozzleis effected by a throttle adjustment screw 85a. Interaction of plenumchamber 64 and the serpentine path function to convert the velocity ofthe liquid into a static pressure having a very small velocitycomponent. The distribution bafile in combination with the plenumchamber and serpentine path establish a smooth, even liquid flow acrossthe length of the orifice. This even flow maintains a uniform liquidpool across the length of longitudinal cavity 7 0.

The direction of rotation of the developer roller, as indicated by arrow90, allows the roller surface to capillarily pick up liquid developerfrom pool 71 and carry it toward the top of the roller as a liquidcoating thereover, for application to the underside of copy sheet 22.While rotation of the roller surface through the liquid pool is probablythe most important method of coating the developer roller, twoadditional coating methods are also employed with the above nozzleconstruction.

In the first additional method, the small velocity component of theliquid developer flowing through longitudinal orifice 68 follows theunderside of baffie 72 in a generally laminar flow and is directedtoward the top of the developer roller. This laminar velocity componentnot only reaches out to coat the roller surface just before applicationto the copy sheet, but also conditions the surface by impinging upon itwith sufficient force to wash out old liquid developer which has beenpartially depleted of toner particles during the last roller revolution.The conditioned roller is thus coated with fresh liquid developer forimmediate application to the copy sheet.

The second additional technique utilizes the gap between arcuate wall 58of shoe 60 and the surface of the developer roller. The gap communicateswith liquid pool 71 and the liquid developer tends to flow therethroughunder gravitational influence. The downward flow is counter influencedby the upward rotation of the roller surface and the capillary actionbetween the surface and the liquid developer filling the gap. Movementof liquid through the gap in one direction and movement of the rollersurface in the opposite direction functions to thoroughly wet thesurface with developer.

In accordance with the invention, it should be noted that the proximityof the area at which the roller surface is coated with developer to thearea at which the developer is applied to the copy sheet surface, aidsthe roller surface in retaining a heavy liquid developer film.

The combination V shaped copy sheet guide and shield 34 is disposeddirectly above the nozzle and is supported by sidewalls 74 and 76. Theguide comprises an upper leg 96 and lower leg 98 defining a longitudinalslot 100 at the apex of the V. A copy sheet passing between rollers 30and 32 is deflected by the appropriate guide leg and guided to andthrough the slot. As the sheet exits from the slot, proper alignment isestablished for wetting contact between the leading edge of the copysheet and the roller surface. Subsequently, the roller carries theleading edge over the top surface so that the underside of the sheet istangential to the roller surface and floats on the liquid coating overthe flat crests of circular ridges 57a.

A pair of upper and lower overhangs 102 and 104, respectively, formingacute angles with legs 96 and 98, shield the copy sheet fromfortuitously misdirected liquid developer droplets which may otherwisecause spotting. The lower overhang also shields the underside of thecopy sheet from liquid developer which may migrate rearwardly over thenozzle. Excess liquid developer which may drip from the shield elementsis collected in container 78 for recirculation by pump 82 back to thenozzle. In addition, container 78 collects overflow from the liquid pooland also collects liquid which trickles through the liquid gap 62.

The transport rollers, the developer roller, and the drying roller areall driven by a main driving gear 106 which in turn is driven by motormeans, not shown. The main driving gear drives a gear 108 fastened toroller 32, a gear 110 secured to roller 38 and a gear 112 secured toroller 54 for movement of the entrance transport, friction, and exittransport rollers respectively. An intermediate gear 114 is driven bygear 110 to ultimately drive the drying roller 40 through a gear 116secured thereto. Intermediate gear 114 also drives roller 48 through anintegral gear 118.

It is obvious that upon study by those skilled in the art the disclosedinvention may be altered or modified both in physical appearance andconstruction without departing from its inventive concept. Therefore,the scope of protection to be given this invention should not be limitedby the embodiment described above, but should be determined by theessential descriptions thereof.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. Apparatus for applying liquid developer composition to a copy sheetbearing a latent electrostatic image, comprising: a supply of liquiddeveloper; a peripheral surface over which it is desired to uniformlydistribute a coating of said liquid developer composition; developerretaining means adjacent said roller including a longitudinal shoeforming a longitudinal cavity partially defined by a segment of saidroller peripheral surface substantially above said axis; meansdelivering a quantity of liquid developer from said supply to saidcavity, forming a longitudinal pool of liquid developer therein; saidroller surface moving through said pool and capillarily picking-up saidliquid developer in a uniformly distributed coating; said longitudinalshoe having a shape complementary to the surface of the developer rollerand extending through a substantial area of are beneath said cavity andclosely adjacent but non-contiguous with a side segment of said rollersurface thereby defining a narrow liquid-filled gap communicating withsaid cavity; said gap being maintained sufliciently narrow to preventsubstantial loss of liquid from said pool during rotation of saidroller, and means transporting said copy sheet into contact with saidcoating for application of liquid developer thereto.

2. The apparatus as set forth in claim 1 wherein the peripheral surfaceof said roller moves upwardly at said gap, capillarily picking-up saidliquid developer and substantially overcoming the gravitationallyinfluenced downward liquid flow therethrough.

3. Apparatus for applying liquid developer composition to a copy sheetbearing a latent electrostatic image, comprising: a supply of liquiddeveloper; a rotating developer roller having a horizontal axis and aperipheral surface over which it is desired to uniformly distribute acoating of said liquid developer composition; developer retaining meansadjacent'said roller forming a longitudinal cavity, partially defined bya segment of said roller peripheral surface, substantially above saidaxis; a pump having a liquid inlet communicating with nozzle meansdischarging said liquid developer into said cavity, forming alongitudinal pool of liquid developer therein; said roller surfacemoving through said pool and capillarily picking-up said liquiddeveloper in a uniformly distributed coating; said nozzle meanscomprising a member having a length substantially equal to the length ofsaid cavity; said member defining a longitudinal plenum chamber havingan inlet at one location therealong receiving liquid developer from saidpump outlet, and an outlet extending the length thereof; said memberalso defining a longitudinal discharge orifice communicating with saidchamber outlet for discharging liquid developer into said cavity; liquiddistribution means interior of said chamber for substantially equalizingliquid flow along said orifice; 'bafile means above said orificeextending partially over and comprising one wall of said cavity; saidbaffle means directing a portion of liquid discharged from said orificetoward the top surface of said developer roller in a generally laminarflow; and means transporting said copy sheet into contact with saidcoating for application of liquid developer thereto.

4. The apparatus as set forth in claim 3 wherein said transport meansinclude copy sheeet guide means disposed behind and substantially levelwith the top surface of said roller; said guide means guiding a surfaceof said copy sheet into tangentially skimming relationship with the topof said developer roller.

5. The apparatus as set forth in claim 4 wherein said guide meanscomprise a longitudinal fabrication having a portion of V shapedcross-section defining a slot along the apex thereof; said V portionreceiving said copy sheet and guiding it through said slot toward saiddeveloper roller; and wherein each end of said V portion carries shieldmeans for shielding said copy sheet from rearwardly migrating andfortuitously dispersed.

6. Apparatus for applying liquid developer composition to a copy sheetbearing a latent electrostatic image, comprising: a supply of liquiddeveloper; a rotating developer roller having a horizontal axis and aperipheral surface over which it is desired to uniformly distribute acoating of said liquid developer; unitary, substantially rigid developerretaining means adjacent said roller forming a longitudinal cavitypartially defined by a segment of said roller peripheral surfacesubstantially above said axis; means delivering a quantity of liquiddeveloper from said supply to said cavity, forming a longitudinal poolof liquid developer therein; said roller surface moving through saidpool-and capillarily picking up said liquid developer in a uniformlydistributed coating; said liquid delivery means comprising a pump havinga liquid inlet communicating with said supply of liquid developer and aliquid outlet; a nozzle coupled to said liquid outlet for dischargingsaid liquid developer into said cavity and for directing at least aportion of said liquid at the roller surface generally in the directionof its movement for conditioning thereof, and means transporting saidcopy sheet into contact with said coating for application of liquiddeveloper thereto.

7. The apparatus as set forth in claim 6, wherein said nozzle includes alongitudinal discharge orifice for dis charging said liquid developeralong substantially the entire length of said cavity and forestablishing a velocity component having a direction intercepting saidroller surface.

References Cited UNITED STATES PATENTS 3,276,424 9/1966 Marx et al.118-637 3,369,523 2/1968 Naumann 118-637 3,112,685 12/1963 Fluke118410XR 3,113,884 12/1963 Kohler 118-410 XR 3,124,484 3/ 1964 Magnusson118-637 3,245,381 4/1966 Brenneisen et al. 1l8637 3,307,466 3/1967Fukuda 118-259 XR PETER FELDMAN, Primary Examiner US. Cl. X.R.

